Most hydraulic or pneumatic systems employ elastomeric and/or plastic seals to prevent or control the flow of fluid through the clearance between two closely fitted surfaces. The sealed surfaces can be generally cylindrical surfaces, such as a piston and cylinder combination, a piston rod and rod guide combination, or a rotating shaft and housing combination. Additionally, the closely fitted surfaces may be static or dynamic with respect to each other, either in the axial or circumferential direction.
One type of seal used in seal assemblies is an O-ring. In general, the O-ring is installed in a machined groove extending into one of the two surfaces to be sealed. Typically, the cross section of the O-ring is at least slightly larger than the cross section of the receiving groove such that when the two surfaces are brought together, a portion of the cross section of the O-ring is squeezed, thereby absorbing the tolerance backup between the surfaces.
In relatively low pressure applications (i.e., when the fluid being sealed exerts little or no pressure or force on the seal), as the O-ring is squeezed, the O-ring exerts a return force against the mating surface and the groove. In this manner, the O-ring firmly contacts both the mating surface and the groove to create a barrier for blocking the passage of fluid between the surfaces. For applications in which higher pressures are exerted on the O-ring, the sealing force of the squeezed O-ring is augmented by the system fluid pressure. In some conventional applications, one or more generally rigid back-up rings (or “anti-extrusion rings”) are provided to support the O-ring, particularly to prevent the softer elastomeric O-ring from being damaged as a result of its being forced or extruded into the clearance between the sealed surfaces.
To facilitate the installation of the backup ring into a typical seal groove, the backup ring is commonly split or cut completely through at one place along its circumference. Of course, once the backup ring is cut, it no longer provides a complete circumferential plane of protection for the O-ring. As a result, many conventional backup rings tend to separate at the split, particularly in high pressure applications, thereby permitting the softer O-ring to extrude into the resulting gap in the backup ring and possibly causing deterioration.
Accordingly, it is desirable to provide a seal assembly with a backup ring of a simple design that is effective for a variety of different sealing applications, including high pressure applications. It is further desirable to provide backup rings that more effectively prevent deterioration and/or extrusion of the O-rings. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.